A waste heat boiler (WHB) in a green ammonia plant recovers heat from the synthesis gas to generate steam and power turbines. WHBs are critical pieces of equipment that need to perform reliably in harsh conditions.
How it works
The WHB cools the hot synthesis gas that exits the ammonia converter
The heat from the gas is used to generate steam for the process and to power turbines
The WHB can be designed with one or two compartments, and can be combined with a steam superheater
Challenges
The high pressures and high hydrogen and ammonia contents of the synthesis gas can make heat recovery challenging
Severe temperature swings can cause tube failures
Corrosion under deposits in the hot zone can cause tube failures
Solutions
Thermal protection
The WHB can be designed with thermal protection to avoid long-term degradation from high temperatures and corrosive gases
Floating head design
A floating head design allows the tube bundle to expand and contract more freely during temperature changes
Bayonet tube design
A bayonet tube design keeps low alloy metal parts out of temperature zones where nitriding is a concern
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